Topic 5: Succession

Question 1

Define succession (2 points)

Answer 1

1. The sequence of changes in {an ecosystem / a community / organisms /species / plants} over a period of time,
2. that eventually form a climax community.

Note: If primary succession you could add that it starts with bare rock

Question 2

Ecosystems have developed from bare rock over thousands or millions of years through the process of __________.

Answer 2

succession

Question 3

Where does primary succession happen? (1 point)

Give 3 examples

Answer 3

1. Primary succession happens on newly formed habitats that have NEVER PREVIOUSLY HAD ANY living organisms there.
   e. g. bare rock, sand dunes, open water

Question 4

Explain the Pioneer Phase (Colonisation) (4 points)

Answer 4

(first phase of primary succession)

1. The process starts on newly formed habitats where there have never been a community before.
   (i. e. bare rock, volcanic ash, coastal sand or shingle, mining deposits.)
2. Pioneer species, such as lichens and algae start to grow.
3. These species can live in the harsh conditions
   – no soil, little water and minerals, wind exposure, extremes of temperature.
4. They add organic matter (humus) to the soil as they die and decompose, and with the substrate (rock, ash etc), start to produce a thin soil (there is a change in the abiotic conditions).

Question 5

Explain development (phase) (3 points)

Answer 5

(second phase of primary succession)

1. MOSSES can now grow (change in the biotic conditions). They add more organic matter to the soil, the soil can now hold more water and mineral ions.
2. Small, shallow-rooted plants can now grow (e.g. grasses), so FURTHER ORGANIC MATERIAL ADDED to soil.
3. As abiotic conditions in the habitat improves, larger, taller plants can grow, which OUT-COMPETE the shorter plants (they replace the previous community)

Question 6

Give the properties of a climax community (4 properties)

Answer 6

(third/final stage of succession)

1. A community dominated by trees (normally) is established
2. Remains {unchanged / stable} unless abiotic or biotic conditions in the habitat change
3. It is self-sustaining
4. Many different types of species and niches (high biodiversity)
   (however this does still depend on the climatic conditions and species available)

Question 7

Define climax community (2 points)

Answer 7

1. The final stage of succession.

2. It is normally STABLE, SELF-SUSTAINING and often has one or two DOMINANT SPECIES.

Question 8

Why is a climax community stable? (4 points)

Answer 8

1. There is high biodiversity. (Many species of both animals and plants)
2. There is interaction between species
3. There is a balanced equilibrium of species
4. There is a dominant plant species
   (one that exerts an overriding influence over the rest of the plant, microbe and animal species, usually largest and most abundant plant species)

NOTE: it remains unstable if no change to environment (e.g. from human influence or natural disaster)

Question 9

The _______ (biomass) and _______ (biodiversity) of living organisms increases as the succession proceeds, but the highest biodiversity is not always at the _______ __________ stage.

Answer 9

quantity

variety

climax community

Question 10

Key Summary: Describe the process of succession (7 steps)

Answer 10

1. PIONEER COMMUNITY of lichens and algae which are able to grow in {little / no} soil or bare rock COLONISE the area.
2. They break up rock fragments to form {thin / shallow} soil.
3. Plants with short roots and mosses are able to grow in SHALLOW SOIL, so number of plant species increases.
4. Soil structure CHANGES, it becomes deeper, able to hold water /minerals, as plants die and decay and humus increases.
5. Improved soil for plants enables {trees / shrubs} to grow.
6. Larger/taller plants OUTCOMPETE pioneer species/low growing plants.
7. A stable CLIMAX COMMUNITY with dominant species forms.

Question 11

Where does secondary succession occur? (1 point)

Give 3 examples

Answer 11

1. Occurs on BARE, EXISTING SOIL where vegetation has been cleared (primary succession has been interrupted).

Examples: (Any 3)

• after forest fire
• ploughed field
• shifting river courses
• volcanic eruption,
• hurricane
• flooding
• grazing has been stopped

Question 12

___________ succession doesn’t have to start from scratch.

Even though the soil is bare, there is soil present.

This means that there will be _______ _______, more _______ ________ _______, dormant seeds, roots and soil organisms

The development time can depend on a number of on factors:

• _________
• _______
• soil fertility
• animal species present

Answer 12

Secondary

organic matter

water holding capacity

temperature

rainfall

Question 13

In secondary succession, different species make up the new community:

• different _______ have been created
• different _______ species grow

As a result, the secondary climax community can be ________ from the original.

Answer 13

niches

pioneer

different

Question 14

Define deflected succession (1 point)

Give 3 examples

Answer 14

1. A community that remains stable only because human {activity/management} prevents succession from running its course.

Examples: (any 3)

• Managed fires
• pond dredging
• golf courses
• playing fields (mowing)
• grazed fields

Question 15

A climax community which is partly the result of human intervention is known as __________.

Answer 15

plagioclimax